1. Field of the Invention
The present invention relates to a semiconductor device and, more particularly, to a structure of a semiconductor device capable of determining the degree of contact between cooling means and the semiconductor device.
2. Description of the Background Art
Conventionally, in a semiconductor device having a large heating value, to cool the semiconductor device, a cooling device is attached to the semiconductor device. In order to improve the cooling efficiency, good contact between the semiconductor device and the cooling device (both of them are in contact with each other so that an effect of the cooling device can be sufficiently displayed) is important.
In the case where the semiconductor device and the cooling device are closely in contact with each other (in the case of good contact), heat from the semiconductor device is sufficiently transmitted to the cooling device, and it means that the semiconductor device is cooled effectively. On the other hand, when the semiconductor device and the cooling device are in contact with each other but not closely attached (in the case of poor contact such as a case where a space exists partly or a case where areas to be in contact are deviated from each other), the semiconductor device is not sufficiently cooled by the cooling device. Consequently, a problem such as erroneous operation due to thermal runaway of the semiconductor device or destruction or the like of the semiconductor device occurs.
Conventionally, to improve the contact between the semiconductor device and the cooling device, a method of making the semiconductor device and the cooling device in contact with each other with pressure by using a resilient member such as a spring, or a method of providing a recess and a projection which are fit to each other in the contact portion of the semiconductor device and that of the cooling device to enlarge the contact area between the semiconductor device and the cooling device is employed.
However, in the cases such that a deviation occurs at the time of attaching the cooling device to the semiconductor device, or a positional deviation occurs between the cooling device and the semiconductor device by an impact from the outside after being fixed, except for actually detecting an increase in temperature of the semiconductor device, there is no method of detecting deterioration in the cooling efficiency of the cooling device. Consequently, there are problems such that erroneous operation of the semiconductor device, and deterioration or destruction in the semiconductor device due to a sharp temperature rise cannot be avoided.
An object of the invention is to provide a semiconductor device capable of knowing deterioration in cooling efficiency of a cooling device by a method other than a method of detecting a temperature rise in the semiconductor device.
According to the invention, a semiconductor device which discharges heat by being in contact with cooling means, includes: contact means provided in a mounting face on which the cooling means is to be mounted so that its level becomes almost the same as that of the mounting face; and measuring means provided between the cooling means and the contact means, for measuring the degree of contact between the cooling means and the semiconductor device.
By enabling the degree of contact between the cooling means and the semiconductor device to be measured, when a deviation occurs in attachment between the cooling device and the semiconductor device, the deviation can be detected before the temperature of the semiconductor device rises. As a result, when it is determined that a deviation occurs in attachment between the cooling device and the semiconductor device, by regulating or interrupting the supply of power to the semiconductor device, erroneous operation of the semiconductor device and deterioration and destruction in the semiconductor device due to a sharp temperature rise can be avoided. Thus, the operation reliability of the semiconductor device can be improved.
In the invention, preferably, the contact means has a first contact terminal and a second contact terminal which come into electric contact with the cooling means, and the measuring means forms a closed circuit in which the first and second contact terminals serve as switching elements which come into contact with the cooling means, and measures whether the closed circuit is closed or not by using the switching elements. By enabling whether the closed circuit is closed or not to be detected and separately providing a resetting circuit, a power supply circuit can be controlled.
In the invention, preferably, the contact means has a first contact terminal and a second contact terminal which come into contact with the cooling means via an insulating member, and the measuring means forms a closed circuit in which the first and second contact terminals serve as capacitative elements and measures electrostatic capacity of the closed circuit. By enabling the change in the electrostatic capacity in the closed circuit to be measured, a delay circuit obtained by combining the closed circuit and a resistor can be constructed, and the supply of power to the semiconductor device can be controlled on the basis of determination of delay time.
In the invention, preferably, the semiconductor device has a semiconductor chip, a plurality of internal electrodes, a plurality of electrodes provided for the semiconductor chip, a plurality of conductors for connecting the electrodes and the corresponding internal electrodes to each other, and a package member for sealing the semiconductor chip, the internal electrodes, the electrodes, and the conductors with a resin, and each of the first and second contact terminals is obtained by exposing a part of selected one of the conductors from the package member in the mounting face on which the cooling means is to be mounted.
Since each of the first and second contact terminals is formed by using a conductor as a part of components of the semiconductor device conventionally used, a semiconductor device having first and second contact terminals can be obtained without employing a new fabrication step while avoiding an increase in cost of providing the first and second contact terminals.
In the invention, preferably, the semiconductor device includes a semiconductor chip, a plurality of internal electrodes, a plurality of electrodes provided for the semiconductor chip, a plurality of conductors for connecting the electrodes and the internal electrodes to each other, and a package member for sealing the semiconductor chip, the internal electrodes, and the conductors with a resin, and each of the first and second contact terminals is obtained by exposing a part of selected one of the internal electrodes from the package member in the mounting face on which the cooling means is to be mounted.
Consequently, since each of the first and second contact terminals is formed by using the internal electrode as a part of components of the semiconductor device conventionally used, a semiconductor device having first and second contact terminals can be obtained without employing a new fabrication step while avoiding an increase in cost of providing the first and second contact terminals.
In the invention, preferably, a conductive paste is provided on and around the first and second contact terminals. With the configuration, the stable contact between the first and second contact terminals and the cooling device is achieved, and conduction between the first and second contact terminals and the cooling device can be obtained with reliability.
According to the invention, there is provided a method of manufacturing a semiconductor device which discharges heat by being in contact with cooling means, including a step of sealing components of the semiconductor device with a package member, the components being a semiconductor chip, a plurality of internal electrodes, a plurality of electrodes provided for the semiconductor chip, and a plurality of conductors for connecting the electrodes to the corresponding internal electrodes, and a removing step of removing a mounting face side with which the cooling means comes into contact of the package member by a predetermined thickness, each of the conductors being formed in a loop so as to open toward the mounting face side, and the removing step includes a step of forming a contact terminal made from an exposed area of the conductor on the mounting face side of the package member by removing the package member so that the apex of the loop of the conductor is exposed.
Consequently, in the case where it is difficult to form contact terminals exposed in the surface by a conventional manufacturing method such as a case where a film of resin is formed on the surface of the conductor, the contact terminal exposed in the surface with reliability can be formed.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.